How to check for presence of scroll bars in TJvTreeView

Question

I am trying to position something w.r.t. a TJvTreeView, and I would like to know both the width and presence of the vertical scroll view. Does anyone know the canonical way to do that? Or failing that, any way that works?

Answer 1

Test for the presence of the WS_VSCROLL window style:

HasVertScrollBar := (GetWindowLongPtr(hWnd, GWL_STYLE) and WS_VSCROLL) <> 0;

To find the width of system scroll bars, call SystemParametersInfo passing SPI_GETNONCLIENTMETRICS.

var
  ncm: TNonClientMetrics;
....
ncm.cbSize := SizeOf(ncm);
Win32Check(
  SystemParametersInfo(SPI_GETNONCLIENTMETRICS, ncm.cbSize, Pointer(@ncm), 0)
);

The scroll bar width can then be retrieved from ncm.iScrollWidth.